1. Field of the Invention
The present invention is directed to a coupling mechanism for operatively connecting a sulky to a motorized vehicle, in particular, to a zero turn walk behind commercial mower. The coupling mechanism controls the tilting of the seat of the sulky during the traversing of a crest or ravine to position the user of the sulky in a proper position for controlling the motorized vehicle.
2.Description of Background Art
Many sulkies for attachment to a motorized vehicle are commercially available. One such motorized vehicle is a zero turn mower which has the ability to lock one of the drive wheels and pivot about the locked wheel so that the turning radius is zero. The available sulkies articulate about a vertical axis extending through the sulky hitch. In addition, the sulkies pitch about a transverse horizontal axis that contains the hitch. Further, the sulkies roll about a longitudinal horizontal axis that contains the hitch. This articulation is necessary so that grass being cut by the mower is cut at a substantially constant height regardless of the ground contour. This freedom of movement is sometimes not comfortable or convenient for the operator. During the traversing of a crest or ravine, the operator may not be conveniently positioned relative to the controls of the motorized vehicle. A conventional sulky may roll from one side to the other as the mower traverses uneven ground and/or is subjected to quick turns.
An operator positioned on a sulky may cause the motorized vehicle to become inclined relative to the sulky merely by his/her weight. The seat of a conventional sulky is normally located behind the wheel axle of the sulky. This will cause the motorized vehicle to pivot upwardly or downwardly about the hitch point depending upon the weight of the operator. Static forces are produced based on the application of the weight of the operator on the sulky. In addition, dynamic forces applied to the sulky by the operator may affect the position of the motorized vehicle relative to the sulky. This may occur when the sulky and motorized vehicle are traveling up a hill. If the operator applies a downward force to the foot rest of the sulky in order to increase the traction of the rear wheels of the motorized vehicle, this causes the front end of the mower to lift up and decreases the distance between the operator and the mower controls.
During a condition wherein the motorized vehicle is cresting a hill, the angle formed between the sulky and the motorized vehicle increases the distance between the operator and the motorized vehicle controls. This amount of backward pitch permitted by a conventional sulky may displace the controls beyond the normal reach of the operator. This would cause the operator to stretch uncomfortably in order to reach the controls. In addition, the seat tilts rearwardly and extends the distance the operator must reach for the controls.
The primary factor which controls the amount of articulation, pitch and roll of a sulky is the location of the hitch point on the motorized vehicle. FIGS. 4 and 5 schematically illustrate the location of the hitch points of conventional Brand A and Brand B sulkies. As illustrated in FIG. 4, a relatively small angle of 7.9 degrees is provided between the two solid lines which represent the horizontal and the radial distance from the wheel center of the conventional hitch assembly for a sulky. When the sulky illustrated in FIG. 4 is cresting a hill, the wheels 20A of the sulky are moved 2.79 centimeters or 1.1 inches towards the wheels 113A of the motorized vehicle. When the sulky illustrated in FIG. 4 is traversing a ravine, the wheels 20A of the sulky are not moved towards or away from the wheels 113A of the motorized vehicle. The fact that the wheels of the sulky are not linearly displaced a sufficient distance relative to the control handles of the motorized vehicle will result in the operator of the sulky being too close or too far from the control handles as the motorized vehicle traverses a ravine or traverses a crest of a hill.
As illustrated in FIG. 5, a relatively small angle of 15.3 degrees is provided between the two solid lines which represent the horizontal and the radial distance from the wheel center of the conventional hitch assembly for a sulky. When the sulky illustrated in FIG. 5 is cresting a hill, the wheels 20B of the sulky are moved 4.06 centimeters or 1.6 inches towards the wheels 113A of the motorized vehicle. When the sulky illustrated in FIG. 4 is traversing a ravine, the wheels 20A of the sulky are moved 2.29 centimeters or 0.9 inches away from the wheels 113A of the motorized vehicle. Again, the fact that the wheels of the sulky are not linearly displaced a sufficient distance relative to the control handles of the motorized vehicle will result in the operator of the sulky being too close or too far from the control handles as the motorized vehicle traverses a ravine or traverses a crest of a hill.
The design objective of the conventional sulky hitch points is to locate the hitch point as close to the horizontal plane containing the drive wheel axis as possible. This allows the towing force applied to the sulky to approach a maximum and reduces the effects of the towing forces on reducing the drive wheel traction.
Conventional sulky hitches are specifically designed to minimize the angular and radial distances. This minimization allows little or no longitudinal displacement of the sulky relative to the mower as the sulky pitches forward and backward.
The conventional sulkies create a sense of lateral instability when subjected to either uneven ground, high friction surfaces and/or exiting from a zero turn application. There are two factors which dictate lateral stability, the maximum roll of the sulky and the location of the footrests relative to the stability triangle of the sulky. The stability triangle is defined by a triangle formed by the center of each sulky wheel and the hitch point. A force applied within the stability triangle will not generate a moment which would cause the sulky to roll to the side of the applied force. A force applied outside of this stability triangle will create a moment and cause the sulky to roll towards the side on which the force acts.
Conventional sulkies permit about 25.4 centimeters or 10 inches of vertical displacement or approximately 15.5 degrees of roll. This amount of roll is a function of the type of hitch, e.g., ball joint, and the tolerance or play between the hitch components. This large roll angle may be inconvenient for the operator. During a high speed operation, this roll angle will add to a sense of instability due to the increased lateral acceleration on the operator.
The large rolling displacement permitted by the conventional sulky may not easily be countered by the operator. The operator may attempt to correct this situation by applying a force to the footrest that has titled upwardly. However, this force will have little or no effect to regain equilibrium of the sulky because the force may be applied within or substantially adjacent a side of the stability triangle. Either no moment will be generated or the moment caused by this force will be insufficient to roll the sulky in the opposite direction and equilibrium will not be regained.